A new study found adjustments made to global surface temperature readings by scientists in recent years "are totally inconsistent with published and credible U.S. and other temperature data."

"Thus, it is impossible to conclude from the three published [global average surface temperature (GAST)] data sets that recent years have been the warmest ever – despite current claims of record setting warming," according to a study published June 27 by two scientists and a veteran statistician.

The peer-reviewed study tried to validate current surface temperature datasets managed by NASA, NOAA and the UK's Met Office, all of which make adjustments to raw thermometer readings. Skeptics of man-made global warming have criticized the adjustments.

Climate scientists often apply adjustments to surface temperature thermometers to account for "biases" in the data. The new study doesn't question the adjustments themselves but notes nearly all of them increase the warming trend.